Electric arc extinguishing means



y 1949 K. LERSTRUP 2,477,189

ELECTRIC ARC EXTINGUISHING MEANS Filed Dec. 5, 1946 wz/ W22 ATTO RN ET Patented July 26, 1949 ELECTRIC ARC EXTINGUISHING MEANS Karl Lerstrup, Milwaukee, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application December 5, 1946, Serial No. 714,277

3 Claims. 1

This invention relates to electric are extinguishing means and more particularly to are chutes. The invention may be utilized in various relations one of which will be described hereinafter. The principal object of the invention is the provision of new and improved arc extinguishing means.

One way in which an electric arc may be treated to extinguish it is to provide barriers in an arc chute so constructed and arranged that as the arc moves in the arc chute the arc is constricted or lengthened or both, by the barriers. Prior proposals while constricting and/or lengthening the arc fall to provide for eiiicient ventilation of the chute. Accordingly, another object of the invention is to provide a construction and arrangement which avoids this disadvantage and provides efficient constricting and/or lengthening of the are along with efficient ventilation thereby to provide more eilicient are extinguishing means.

Another object of the invention is to provide a construction and arrangement in which the provision of ventilating paths through the arc chute is fully utilized and a maximum draft through the arc chute results. A more specific object the invention is the provision of such a construction and arrangement in which elongated, substantially unconstricted portions of the are are subjected to a ventilating draft through the chute.

Other objects will appear hereinafter as the description of the invention proceeds.

The novel features of the invention and how the objects are attained will appear from this specification and the accompanying drawing showing one embodiment of the invention and forming a part of this application, and all of these novel features are intended to be pointed in the claims.

In the drawing:

Fig. 1 is a side elevational view of an electric circuit breaker which includes an arc chute, the latter being in longitudinal midsection, illustrating one embodiment of the invention; and

Fig. 2 is a perspective detail view partly fragmentary and partly broken away, of the arc chute embodied in Fig. 1.

Referring to Fig. l, the circuit breaker here shown comprises a relatively stationary main contact means l0 engageable by relatively movable main contact means ll; intermediate relatively stationary contact means l2 also engageable by the main contact means I and relatively stationary arcing contact means l3 engageable by an upward extension of the main contact means H continuing in an arc horn I l. The

2 arcing contact means I3 is here shown as including an arc runner portion I5 which first extends upwardly and outwardly at an angle away from the arc horn M, then vertically upwardly as an extension 26.

Current may be led to the main contact means I0 and intermediate contact means l2 by a fixed conducting member iii. The conducting member l6 may be connected to a circuit conductor 22 in any suitable way. An arc blowout coil H has its terminals connected to the conducting member l6 and the arcing contact means l3, respectively.

The movable main contact means I l as here shown is carried by a conducting arm I! swingable about a pivot l9 carried by a fixed conducting member 20. The conducting member 20 may be supported, and be electrically connected to a circuit conductor 2i, in any suitable way.

Electrically connected to the conducting member 20, as by a conductor 23, is an arc runner 24 supported in any suitable way and extending diagonally upward toward the left and here shown as having a vertical extension 25.

For extinguishing the are which is formed when the switch is opened as will appear hereinafter. an arc chute 28 is provided. The are chute 28 comprises side walls 29, 30 and end walls 3|, 32. made of any suitable insulating material. The side walls 29, 30 are here shown as defining parallel vertical planes spaced from each other a desired distance and they are wide enough so that the end walls 3!, 32 at least span the distance between the arc runner extensions 25, 26. The are chute 2B is open at the bottom and top thus providing a vartically extending space in which the arc can move upwardly and into which air can enter at the bottom and move upwardly and be discharged at the top. The are chute 28 is considered open at the top if an updraft of air can take place even though screens or the like (not shown) he provided at the top if desired.

Projecting from the inside surface of the side wall 29 toward the side wall 30 is a set of a plurality of insulating barriers 35 having free marginal ends 36 spaced from the side wall 30. At their upper ends the marginal free ends 36 are only a relatively small selected distance from the inside surface of the side wall 30 whereas at their lower ends the marginal free ends 36 are here shown as abutting the inside surface of the side wall 29. As here shown the marginal ends 35 are curvilinear so that for equal successive increments of downward progression the recession 7 from the side wall 30 is at an increasing rate, but

the marginal free ends may be given any other desired curvature, or made substantially rectilinear in whole or part.

Projecting from the inside surface of the side wall toward the side wall 29 is a set of a plurality of insulating barriers 31 having free marginal ends 38. At their upper ends the marginal free ends 38 are only a relatively small selected distance from the inside surface of the side wall 29, whereas at their lower ends the marginal free ends are here shown as abutting the inside surface of the side wall 30. The marginal free ends 38 may be formed in the same ways as hereinbefore described with respect to the free marginal ends 36.

In Fig. 2 some of the barriers and margins designated by the numerals 35, 36, 3'! and 38 have letter suffixes for convenience in identifying these parts in connection with the description of the operation, as will appear.

Desirably, the barriers of the sets of barriers 35, 3'! define parallel vertical planes. The barriers of the set of barriers 35 are here shown as equally spaced from each other, and the barriers of the set of barriers 31 are also here shown as equally spaced from each other, but these sets of barriers are displaced laterally relatively to each other so that any given barrier of one set between two adjacent barriers of the other set is spaced a much smaller distance from one of the adjacent barriers than from the other. For example, referring to Fig. 2, the distance d is small relatively to the distance D.

Considering the sets of barriers 35, 31 it will be apparent that while they are interleaved they do not overlap throughout their vertical length but only upwardly from a place where the marginal ends 36, 38 cross over in lateral aspect. Desirably, the upper ends of the arc runners I5, 24, or in this instance the upper ends of the arc runner-extensions 25, 26, extend substantially above the level of the line defined by the crossovers 40.

The entrance space defined by the arc chute 28 is preferably made long enough below the lower ends of the barriers 35, 31 to enclose the switch contacts and arc runners; and the discharge space defined by the arc chute is made of a desired suitable length above the upper ends of the barriers 35, 31 to vent the products of interruption.

The blowout coil i1 is disposed about a magnetic core 4|, the core being here shown as having legs, extending transversely from the ends of the core, and disposed adjacent the outer surfaces of the side walls 29, 30 so as to provide a magnetic field across the arc chute for causing upward movement of the arc. One of these legs, 42, is indicated in Fig. 1.

The operation of the apparatus is as follows. When the parts are in the position shown in Fig. 1 a principal path for electric current may be traced from, for example, the circuit conductor 2| through the conductor 20, arm l8, main contacts H, i0 through the conductor IE to the circuit conductor 22. If the current path is to be interrupted the arm I8 is caused to swing counterclockwise by any suitable means. movement first causes disengagement of the movable main contact II from the stationary main contact 10, without'arcing, leaving a current path through the main contact II and the intermediate contact l2. Further movement of the arm l8 causes disengagement of the main contact ll and the intermediate contact l2, thereby This causing current to flow through the blowout coil l1. Still further movement of the arm It causes disengagement of the arc horn l4 and the arc runner l5, thereby drawing an arc in a substantially horizontal direction, the left hand terminal of the are being transferred from the arc horn [4 to the arc runner 24 when the arm l8 has swung far enough. to its fully open position.

The arc is impelled upwardly rapidly by the magnetic effect of the arc runners i 5, 24 and by the magnetic field provided by the blowout coil I1,

and also by the thermal efiect of the hot arc gases, the vertical arc chute 28 acting as a chimney. Material constriction of the arc begins when it reaches the places 40 where the barriers 35, 31 begin to overlap. The arc, extending between its terminals on the upper ends of the arc runner portions 25, 26, continues to be impelled upwardly, being therebylengthened not only in the general vertical longitudinal plane of the arc chute, that is in the general plane of the paper of Fig. 1, but also in general planes at right angles to that plane since the arc is forced to define a zig-zag path of greater and greater amplitude, by the barriers 35, 31, as the arc moves upward.

Referring more particularly to Fig. 2, it will be noted that the path of the are from the margin 38a to the margin 36a is constricted by reason of the relatively small distance d between the barriers 3'la, 35a, whereas the path of the arc from the margin 36a to the next margin 38!: is relatively unconstricted by reason of the relatively large distance D between the barriers 35a, 31b. The relatively large distance D provides a vertical space between the barriers 35a. and 31b in which air and gas may flow upward at both sides of the arc since in its path from the margin 36a to the margin 38b the arc is spaced from the surfaces of the barriers 35a, 31b. Furthermore, the resistance to upward arc movement in the constricted spaces 11 is substantially greater than in the relatively unconstricted spaces D and hence the arc rises faster in the spaces D than it does in the spaces d. Thus the arc is lengthened upwardly in the spaces D, and the arc portions in the constricted spaces d and the unconstricted spaces D define a path which, projected into a vertical plane, is of zig-zag form.

It will therefore be evident that the construction and arrangement is such that alternate lengthwise portions of the are are constricted and left unconstricted, and, furthermore, that as the arc is moved toward the exit of the chute both the constricted and unconstricted portions of the arc are lengthened, and the path of the arc is of zig-zag form in both horizontal and vertical aspects, so that it is of generally helical form. The constriction and lengthening of the arc increase the electrical resistance of the arc, and along with the ventilation of the chute and the effect thereon on the arc, the latter is promptly extinguished before it reaches the upper ends of the barriers 35, 31.

The are chute 28 need not extend higher than approximately the level of the points 40, but further upward extension is desirable to prevent the are from striking to any adjacent conducting parts and also to get more chimney effect. It will be obvious that the barriers 35, 31 may be supported by the side walls 29, 30 or in any other suitable way.

It will be apparent to those skilled in the art that the illustrated embodiment of the invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than that illustrated, without departing from the spirit of the invention, or sacrificing all of the advantages thereof, and that accordingly the disclosure herein is illustrative only, and the invention is not limited thereto.

It is claimed and desired to secure by Letters Patent:

1. Electric arc extinguishing means for extinguishing an arc impelled to move within an arc chute having an entrance and an exit, said means comprising: two interleaved sets of barriers disposed transversely of said chute and extending in a direction generally from said entrance to said exit, one of said sets comprising a plurality of substantially equally spaced barriers, the other of said sets comprising a plurality of substantially equally spaced barriers, said two sets being laterally displaced so that any given barrier of one set between two adjacent barriers of the other set is spaced a relatively small distance from one of said adjacent barriers and a relatively large distance from the other of said adjacent barriers.

2. Electric arc extinguishing means for extinguishing an arc impelled to move within an arc chute, said means comprising: two interleaved sets of barriers disposed transversely of said arc chute and extending generally longitudinally of said chute, said sets of barriers overlapping onl; from a place intermediate their lengths to the ends of said barriers in the direction of are movement, one of said sets comprising a plurality of substantially equally spaced barriers, the other of said sets comprising a plurality of substantially equally spaced barriers, said two sets being laterally displaced so that any given barrier 01 one set between two adjacent barriers of the other set is spaced a relatively small distance from one of said adjacent barriers and a relatively large distance from the other of said adjacent barriers.

3. Electric arc extinguishing means, comprising: an arc chute having an entrance and an exit and including a first side wall and a second side wall providing therebetween a space into which the arc can be drawn substantially parallel to said side walls and in which the arc can move bodily in a direction substantially parallel to said side walls from said entrance toward said exit; and means for lengthening and constricting the are, said means including two interleaved sets of barriers extending generally in said direction, a first of said sets comprising a plurality of substantially equally spaced barriers projecting from said first wall toward and having their ends spaced from said second wall, a second of said sets comprising a plurality of substantially equally spaced barriers projecting from said second wall toward and having their ends spaced from said first wall, said two sets being laterally displaced so that any given barrier of one set between two adjacent barriers of the other set is spaced a relatively small distance from one of said adjacent barriers and a relatively large distance from the other.

KARL LERSTRUP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

